<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        .box11 {
            width: 300px;
            height: 100px;
            background: #ccc;
            border-radius: 10px;
            margin: 10px;
        }

        .shadow {
            position: relative;
            max-width: 270px;
            box-shadow: 0px 1px 4px rgba(0, 0, 0, 0.3),
            0px 0px 20px rgba(0, 0, 0, 0.1) inset;
        }

        .shadow::before,
        .shadow::after {
            content: "";
            position: absolute;
            z-index: -1;
        }

        .shadow::before,
        .shadow::after {
            content: "";
            position: absolute;
            z-index: -1;
            bottom: 15px;
            left: 10px;
            width: 50%;
            height: 20%;
        }

        .shadow::before,
        .shadow::after {
            content: "";
            position: absolute;
            z-index: -1;
            bottom: 15px;
            left: 10px;
            width: 50%;
            height: 20%;
            box-shadow: 0 15px 10px rgba(0, 0, 0, 0.7);
            transform: rotate(-3deg);
        }

        .shadow::after {
            right: 10px;
            left: auto;
            transform: rotate(3deg);
        }
    </style>
</head>
<body>
<div class="box11 shadow"></div>
</body>
</html>